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A-2 <br /> ACOUSTICAL TERMINOLOGY <br /> NOISE EXPOSURE Lines drawn about a noise source indicating constant levels of <br /> CONTOURS: noise exposure. CNEL and Ld„ contours are frequently utilized <br /> to describe community exposure to noise. <br /> SEL OR SENEL: Sound Exposure Level or Single Event Noise Exposure Level. <br /> The level of noise accumulated during a single noise event, such <br /> as an aircraft overflight, with reference to a duration of one <br /> second. More specifically, it is the time-integrated A-weighted <br /> squared sound pressure level for a stated time interval or event, <br /> based on a reference pressure of 20 micropascals and a <br /> reference duration of one second. <br /> SOUND LEVEL: The sound pressure level in decibels as measured on a sound <br /> level meter using the A-weighting filter network. The A- <br /> weighting filter de-emphasizes the very low and very high <br /> frequency components of the sound in a manner similar to the <br /> response of the human ear and gives good correlation with <br /> subjective reactions to noise. <br /> BBA <br />